The present invention relates to a method and an apparatus for supplying fluorine gas, which are used in supplying fluorine gas to an excimer laser chamber (hereinafter simply referred to as a xe2x80x9cchamberxe2x80x9d) of an excimer laser device or the like.
With respect to techniques for supplying fluorine gas to the chamber of an excimer laser device, for example, JP-A-6-334241 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) describes a technique of using an apparatus comprising a gas bomb filled with fluorine gas, a bomb filled with a rare gas such as krypton, and a bomb filled with a buffer gas such as neon or helium, where out of the gas components forming the excimer laser gas, the fluorine gas and the rare gas each accounting for a small constitutional ratio in terms of gas concentration are supplied through a sub-chamber and the buffer gas having a large constitutional ratio in terms of gas concentration is supplied directly to the chamber. However, in the case of supplying fluorine gas from a gas bomb, the bomb must be housed in a bomb box apart from the excimer laser device to ensure safety and handleability because the bomb contains fluorine gas at a high pressure and the bomb is large and heavy. This is disadvantageous in that the size of the apparatus as a whole becomes very large and fluorine gas filled in the bomb is deteriorated during the long-term storage to impair laser properties of the excimer laser.
On the other hand, for example, International Patent Application No. 5-502981 describes a fluorine gas-generating means using a fluorine-occluding substance such as fluoronickel material in which fluorine is occluded. The fluorine-occluding substance generates fluorine gas by heating and controlling it to a predetermined temperature. Even at a relatively low controlling temperature, the necessary amount of fluorine gas can be generated and at the same time, the generation pressure is low, so that easy handling and high safety can be attained. Furthermore, the generating means can be reduced in the size and since the equilibrated and non-gasified fluorine is in the occluded state, deterioration scarcely occurs even in the long-term storage. However, the pressure of fluorine gas generated using such a fluorine generating means is generally lower than the pressure in the chamber of an operating excimer laser device, therefore, even if fluorine gas is efficiently removed in a practical temperature range, the fluorine gas cannot be introduced directly into the chamber of an operating excimer laser device except for the case where the gas exchange is performed after gas in the chamber is evacuated. To solve this problem, some proposals have been made with an attempt to enable the supply of fluorine gas generated by such a fluorine gas-generating means using a fluorine-occluding substance even at the operating time, to say nothing of the gas exchange time.
Of these, the above-described International Patent Application No. 5-502981 proposes a technique of circulating gas in the chamber by a pump, disposing the above-described fluorine gas-generating means such that it is connectable to the circulation path, and supplying fluorine gas together with the circulating gas to the chamber. JP-A-9-116214 proposes a technique of connecting a bomb of buffer gas such as Ne to the above-described fluorine gas-generating means and supplying the fluorine gas generated under compression of the buffer gas into the chamber. However, generation of fluorine gas using the fluorine-occluding substance cannot be always controlled in a constant and simple manner depending to the temperature and the like. Therefore, the above-described method or apparatus where the fluorine gas-generating means is directly connected to the path for gas supplied to the chamber has difficulty in supplying in a stable manner the necessary amount of fluorine gas with good precision. Moreover, a portion having a high fluorine gas concentration is partially and temporarily generated in the gas supplied to the chamber because fluorine gas in 100% concentration is generated from the fluorine-occluding substance, and this may cause adverse effect such as fluctuation of the laser properties.
On the other hand, U.S. Pat. No. 5,396,514 proposes a technique of introducing fluorine gas generated in the above-described fluorine gas-generating means into a collecting receptacle and then connecting the collecting receptacle with the chamber to disperse the fluorine gas in the chamber, a technique of, similarly to the case in JP-A-9-116214 supra, connecting a rare gas bomb or the like to the collecting receptacle and simultaneously opening the valve between the rare gas bomb and the collecting receptacle and the valve between the collecting receptacle and the chamber to allow the rare gas or the like to compress the fluorine gas to flow out of the collecting receptacle into the chamber, or a technique of, similarly to the case of International Patent Application No. 5-502981 supra, circulating gas in the chamber and connecting the above-described collecting receptacle to the circulating path to thereby supply fluorine gas. However, in these methods or apparatuses, fluorine gas in 100% concentration or a gas unequal in fluorine gas concentration is still directly supplied to the chamber, therefore, the laser properties may fluctuate. This state that the laser properties are unstable disadvantageously continues for a long time particularly when fluorine gas is supplied by dispersion into the chamber, because it takes a long time for the fluorine gas to uniformly disperse in the chamber.
In the case of compressing fluorine gas in the fluorine gas-generating means or collecting receptacle by a buffer gas or rare gas to flow into the chamber, the fluorine gas concentration in the inflow gas is very difficult to always maintain at a predetermined concentration with good reproducibility. Therefore, the laser properties may fluctuate depending on supply of fluorine gas. In the case of circulating the gas in the chamber using a pump, compressor or circulating unit such as a blower and supplying fluorine gas to the circulation path, not only the problem of reproducibility or the like is present but also a problem arises that the fluorine gas supplying apparatus is inevitably complicated due to disposition of the circulating unit or a driving unit for driving it and the effect by using a fluorine-occluding substance in the fluorine gas-generating means is impaired.
On the other hand, in the method for supplying fluorine gas by using a sub-chamber described in JP-A-6-334241 or by using a collecting receptacle described in U.S. Pat. No. 5,396,514, the container is evacuated of residual gas whenever fluorine gas is supplied from the sub-chamber for the purpose of gas exchange in the chamber of an excimer laser device or addition of gas to the operating excimer laser device, and then receives fluorine gas from the fluorine gas-generating means in the container. This is disadvantageous not only due to the cumbersome operation but also in poor profitability, because the residual gas still contains fluorine gas in a certain concentration and also contains rare gas or buffer gas. Furthermore, in these methods or apparatuses for supplying fluorine gas, as a matter of course, fluorine gas cannot be introduced into the container while supplying fluorine gas from the container to the chamber. For example, if fluorine gas in the container runs short during the supply of fluorine gas to the chamber, the supply of fluorine gas must be once interrupted to again introduce fluorine gas into the container. Thus, the fluorine gas cannot be continuously supplied.
The present invention has been made under these circumstances.
A main object of the present invention is to provide a method and an apparatus for supplying fluorine gas when using the above-described fluorine-occluding substance for fluorine gas-generating means, in which a necessary amount of fluorine gas in uniform concentration can be stably and swiftly supplied to the chamber of an excimer laser device or the like even during the operating time as well as the gas exchange time.
Another object of the present invention is to attain the effective use of fluorine gas and rare gas and also enable a continuous supply of fluorine gas.
The above-described problems can be solved and the main object can be attained by a method for supplying fluorine gas of the present invention, comprising:
generating fluorine gas using a fluorine gas-generating means capable of controlling a fluorine-occluding substance to a predetermined temperature, introducing the fluorine gas into a mixing container,
introducing a diluting gas into the mixing container to mix it with the fluorine gas and thereby prepare a fluorine-containing mixed gas (hereinafter simply referred to as xe2x80x9cfluorine mixed gasxe2x80x9d) having a predetermined pressure and a predetermined fluorine gas concentration and reserve in the mixing container,
supplying the fluorine mixed gas to a use point having a pressure lower than the pressure of the fluorine mixed gas.
The diluting gas used here is a single gas of N2, He, Ar or Ne, a mixed gas of He and Ne (buffer gas), or a mixed gas obtained by adding a single gas of Ar or Kr or mixed gas of Ar and Kr (rare gas) to the single gas of He or Ne or mixed gas of He and Ne. In particular, for the KrF excimer laser, Ne or a mixed gas of Ne and Kr is used as the diluting gas. Therefore, according to the supplying method of the present invention, where the fluorine mixed gas is prepared by mixing a low-pressure fluorine gas generated from the fluorine-occluding substance with a high-pressure diluting gas in the mixing container, the above-described predetermined pressure of the fluorine mixed gas prepared can be set higher than the pressure in the destination of supply, such as a chamber, using the pressure of the diluting gas. In the case where the chamber is evacuated, as a matter of course, a necessary amount of fluorine mixed gas can be supplied by the pressure difference without using a circulating unit or the like even to the chamber of an operating excimer laser device.
On the other hand, in the present invention, the fluorine gas concentration in the fluorine mixed gas supplied is defined as the ratio of the total pressure of the fluorine mixed gas prepared to the partial pressure of fluorine gas introduced into the mixed container. Accordingly, for example, by introducing fluorine gas or diluting gas into the mixing container while controlling those pressures to lie in a predetermined ratio, a fluorine mixed gas can be prepared to have a fluorine gas concentration in good reproducibility and always kept essentially at a predetermined concentration. Furthermore, according to the present invention, fluorine gas in 100% concentration introduced from a fluorine gas-generating means is diluted with a diluting gas to prepare a fluorine mixed gas having a low fluorine gas concentration or the fluorine gas is uniformly dispersed because the fluorine mixed gas is reserved in the mixing container, therefore, the fluorine mixed gas can be prevented from generation of partially biased fluorine gas concentration. The influence or the like on the laser properties at the supply of fluorine mixed gas to the above-described chamber can be minimized and stable laser properties can be maintained.
In the present invention, at the preparation of a fluorine mixed gas in the above-described mixing container, if the fluorine mixed gas reserved in the mixing container is extremely reduced, for example, at the first time preparation of a fluorine mixed gas in the mixing container or after gas exchange of the above-described chamber or the like, the fluorine mixed gas may be prepared by evacuating the mixing container in advance, introducing fluorine gas and diluting gas thereinto and mixing them. In this case, a method in which after evacuation of the above-described mixing container in advance, first introducing a diluting gas to a predetermined partial pressure, then introducing fluorine gas and thereafter adding the diluting gas to prepare a fluorine mixed gas may also be used. The pressure in the evacuated mixing container here is of course preferably 0 MPa in theory, however, it is in fact preferably less than 0.01 MPa (absolute pressure, hereinafter the same). This is because if the pressure in the evacuated mixing container is 0.01 MPa or more, the influence of the fluorine mixed gas remaining in the mixing container on the preparation of next fluorine mixed gas in the mixing container cannot be neglected. Thus, the preparation must be performed by taking account of the residual fluorine mixed gas as described below.
That is, in the present invention, the fluorine mixed gas prepared is reserved in the mixing container and then supplied. Therefore, even if the fluorine mixed gas in the mixing container is reduced by the supply, a new fluorine mixed gas can be prepared in the. mixing container without evacuating the fluorine mixed gas in the mixing container but allowing it to remain. By doing so, the fluorine gas or buffer gas in the residual fluorine mixed gas can be effectively used without wasting them and profitability can be increased. In the case of preparing a new fluorine mixed gas while allowing the fluorine mixed gas to remain in the mixing container, the pressure of the residual fluorine mixed gas is, in contrast with the above, preferably 0.01 MPa or more, more preferably in view of profitability, an atmospheric pressure (0.1013 MPa) or more. Incidentally, as the pressure of the residual fluorine mixed gas is higher, a larger amount of fluorine mixed gas remains in the mixing container and this is more profitable, however, if it is excessively high, fluorine gas cannot be efficiently introduced from the fluorine gas-generating means at the preparation of a new fluorine mixed gas. At present, the upper limit is substantially on the order of from 0.2 to 0.3 MPa.
In either case where the mixing container is previously evacuated and then a new fluorine mixed gas is prepared as described above or where a new fluorine mixed gas is prepared while allowing the fluorine mixed gas to remain in the mixing container, the new fluorine mixed gas in the third or later preparation counted from the first preparation in the evacuated state may be prepared by introducing fluorine gas and diluting gas into the mixing container at the same partial pressures as in the preceding second time preparation, so that the new fluorine mixed gas prepared can have the same fluorine gas concentration and pressure (total pressure) as the fluorine mixed gas prepared the second time. However, in the case of preparing a new fluorine mixed gas while allowing a part of the previously prepared fluorine mixed gas to remain in the mixing container, when the preparation precedent to the preparation of a new fluorine mixed gas is the first time preparation performed in the state where the mixing container is evacuated, namely, when a new preparation in the presence of the residual fluorine mixed gas is performed for the first time at the second time preparation subsequent to the first time preparation, if fluorine gas is introduced at the same partial pressure as in the first time preparation and at the same time, a fluorine mixed gas having the same total pressure as in the first time preparation is prepared, the fluorine gas concentration differs between the newly prepared fluorine mixed gas and the precedently prepared fluorine mixed gas.
In such a case, for equalizing the fluorine gas concentration between the precedently prepared fluorine mixed gas and the newly prepared fluorine mixed gas, a method of setting the partial pressure of fluorine gas introduced at the preparation of a new fluorine mixed gas to be the same as the partial pressure of fluorine gas introduced into the above-described mixing container at the preparation of the precedent fluorine mixed gas, or a method of setting the total pressure of the precedently prepared fluorine mixed gas and the total pressure of the newly prepared fluorine mixed gas to the same constant value may be used. In the former method, the total pressure of the precedently (first time) prepared fluorine mixed gas and the newly (second time) prepared fluorine mixed gas may vary, however, the partial pressure of fluorine gas introduced into the mixing container needs not be changed and the operation of introducing fluorine gas from the fluorine gas-generating means can be facilitated. On the other hand, in the latter method, the partial pressure of fluorine gas introduced into the mixing container must be changed but by setting the total pressure of fluorine mixed gas prepared this time to be the same as before, the total pressure of fluorine mixed gas as a whole can be made constant in every preparation such that the operation of supplying to the use point can be facilitated.
The supplying method of the present invention may also be applied to the case where a diluted fluorine gas is required, for example, in the manufacturing process of semiconductors. However, on taking account of the above-described circumstances, the supplying method of the present invention is particularly suitably used for supplying the above-described fluorine mixed gas to a chamber of an excimer laser device. In this case, needless to the case of performing gas exchange after evacuating the above-described chamber, by setting the total pressure of fluorine mixed gas prepared in the above-described mixing container to be higher than the operating pressure in the chamber, the fluorine mixed gas can be supplied to the chamber using the pressure difference even when the excimer laser device is operating, and the operation of the excimer laser device can be continuously and stably maintained. In the case where the mixing container is provided with a holding container as described later, the pressures of the mixing container and the holding container are set to be higher than the pressure in the chamber.
In the supplying step of fluorine mixed gas to the chamber of an excimer laser device, the amount and pressure of fluorine mixed gas in the above-described mixing container are preferably adjusted such that they can respond to at least a single operation of gas adding step where fluorine mixed gas is supplied in the state that the chamber is at an operating pressure and at least one operation of gas exchange step where fluorine mixed gas is supplied after the chamber is evacuated, or can respond to two or more operations of gas addition. In other words, in the supplying method of the present invention, the amount and the pressure of fluorine mixed gas in the mixing container are preferably adjusted such that the fluorine mixed gas reserved in the mixing container by one preparation can satisfy at least a single supply for gas addition to the chamber and at least a single supply for subsequent gas exchange of the chamber, or can satisfy two or more supply for gas addition. Even in such a case, for example, if the pressure of fluorine mixed gas in the mixing container decreases due to a single or multiple times supply for gas addition to the chamber, and the gas addition to chamber using the pressure difference cannot continue but gas exchange in the chamber is necessary, the fluorine mixed gas may be supplied after evacuating the chamber as described above to perform the gas exchange.
In the supplying method of the present invention, a holding container may be provided to the mixing container and the fluorine mixed gas prepared in the mixing container may be introduced and reserved in this holding container and supplied to the use point, so that a new fluorine mixed gas can be prepared by introducing fluorine gas and a diluting gas into the mixing container while supplying the fluorine mixed gas from the holding container to the use point. Thus, continuous supply of fluorine gas can be attained. In this case, the valve between the holding container and the mixing container is naturally closed at the supply of fluorine mixed gas introduced into the holding container.
The apparatus for supplying fluorine gas of the present invention is described below. The apparatus comprises a fluorine gas-generating means capable of generating fluorine gas by controlling a fluorine-occluding substance to a predetermined temperature, and a mixing container for preparing a fluorine mixed gas by introducing and mixing the fluorine gas generated and a diluting gas and holding the fluorine mixed gas prepared. According to the supplying apparatus of the present invention, a fluorine-occluding substance is used for a fluorine generating means, therefore, the size of the apparatus as a whole can be decreased and handleability can be improved. At the same time, by supplying a fluorine mixed gas with an appropriate concentration and pressure prepared and reserved in the above-described mixing container to a destination of the supply such as the above-described chamber, the supplying method of the present invention can be practiced.
The above-described fluorine gas-generating means comprises a fluorine gas-generating container for holding the above-described fluorine-occluding substance, a heating means such as heating wire provided in the periphery of the fluorine gas-generating container, and a temperature controlling means for controlling the heating temperature, in which fins are provided in the above-described fluorine gas-generating container. In the case where the fluorine gas-generating container is heated from outside by the above-described temperature controlling means, the rate of heat transfer to the fluorine-occluding substance can be increased through the fins and thereby the temperature of the fluorine-occluding substance can be exactly and swiftly controlled. The heating means such as heating wire may be disposed in the periphery of the generating container or may be integrated into the inside of the generating container. When a cooling means for cooling the periphery of a valve provided on the above-described fluorine gas-generating container is disposed in addition to the heating means and the temperature controlling means described above, the heat given to the fluorine gas-generating container at the time of generation of fluorine gas may be prevented from propagating to the valve. Furthermore, when a mixing accelerating means for accelerating the mixing of the above-described fluorine gas introduced into the mixing container with a diluting gas is disposed, the time necessary for the preparation may be shortened and at the same time, a fluorine mixed gas free of biased fluorine gas concentration can be produced and supplied.
In the supplying apparatus of the present invention, as described above, a holding container may be provided with the mixing container, so that a new fluorine mixed gas can be prepared in the mixing container while supplying fluorine mixed gas from the holding container. Furthermore, a plurality of the above-described mixing containers may be disposed such that introduction of the fluorine gas and a diluting gas can be selectively performed among those mixing containers, and supply of the above-described fluorine mixed gas prepared can be selectively performed. Also in this case, a new fluorine mixed gas may be prepared by introducing fluorine gas and diluting gas into at least one mixing container while supplying fluorine mixed gas from at least another mixing container. Thus, in either case, the preparation and supply of fluorine mixed gas can be performed in parallel and the fluorine gas can be. continuously supplied. Of course, a plurality of mixing containers each provided with a holding container may also be disposed. Furthermore, a plurality of fluorine gas-generating means may be disposed such that fluorine gas can be introduced to a mixing container selectively from these fluorine gas-generating means. In this case, fluorine gas can be generated and stored in at least one fluorine gas-generating means while introducing fluorine gas generated in at least another fluorine gas-generating means into the mixing container, or fluorine gas generated may be simultaneously introduced into the mixing container. Thus, the introduction of fluorine gas into the mixing container can also be continuously performed.